Technology group Wärtsilä has completed what it describes as the world's first demonstration of a large-scale engine running on 100% pure hydrogen, with the test conducted at its laboratory in Bermeo, in northern Spain, and connected directly to Spain's national electricity grid.

The milestone, announced on 11 June 2026, centres on the Wärtsilä 31H2 engine, which the company identifies as the world's largest pure hydrogen engine. The demonstration moves beyond the concept of hydrogen-ready equipment to show that an engine-based power generation system can operate on entirely hydrogen fuel under real grid conditions.

The Engine and the Test

The Wärtsilä 31H2 is part of the Wärtsilä 31 platform, which the company describes as one of the world's most efficient multi-fuel four-stroke engines. Performance verification of the 31H2 variant is currently underway at the Bermeo site in the Basque Country.

During June 2026, customers from around the world attended the Bermeo facility to witness the engine in operation, an event Wärtsilä characterised as a significant milestone in the commercial validation of the technology. The company said it has started validation of the engine for the purpose of powering Spain's national electricity grid.

The trial builds on Wärtsilä's earlier work, which included the launch of what it described as the world's first large-scale 100% hydrogen-ready engine power plant. The latest test goes a step further by operating on pure hydrogen rather than demonstrating readiness for future use.

What Hydrogen Brings to the Grid

Wärtsilä's rationale for hydrogen-based engine power centres on the challenge of balancing electricity grids that rely heavily on wind and solar generation. Green hydrogen, the company noted, produces no carbon emissions and can store excess renewable electricity generated during periods of high output. When wind or solar generation drops, hydrogen-fuelled engines can then provide dispatchable power to stabilise the system.

With global renewable energy generation set to grow by almost 4,600 gigawatts by 2030, according to figures cited by Wärtsilä, the company argues that flexible technologies capable of filling gaps in supply are becoming increasingly critical to maintaining reliable electricity systems.

Rasmus Teir, Director of Technology Strategy and Decarbonisation at Wärtsilä, said the test represents proof that large-scale hydrogen engines can provide the flexible, dispatchable sustainable power needed to support future renewable energy systems.

"Today, our Wärtsilä 31H2 hydrogen engine is operating on 100% hydrogen and supplying power to Spain's national grid," Teir said. "We have proven the technology is ready. Now, the focus must be on creating the right environment to scale it, underpinned by decisive regulation, investment clarity, and the infrastructure needed to accelerate the growth of renewable energy and sustainable fuels like hydrogen."

Why Spain Was Chosen

Wärtsilä identified Spain as an appropriate location for the trial based on the country's standing as one of the forerunners in renewable energy adoption and its efforts to reduce exposure to fossil fuel price volatility. Those characteristics, the company said, made Spain a strong test bed for demonstrating the future potential of hydrogen technologies.

The Bermeo laboratory, situated in the Basque region, provided the controlled environment in which the engine could be connected to Spain's national electricity infrastructure for the purposes of the demonstration.

Intended Applications

Beyond grid support, Wärtsilä indicated that the Wärtsilä 31-based power plant is designed to serve energy-intensive industries requiring flexible and sustainable power generation. The company specifically cited AI data centres, manufacturing facilities, and broader industrial applications as sectors that hydrogen-fuelled engines of this type could serve. The platform is also described as suited to off-grid environments.

Wärtsilä noted that hydrogen-fuelled Wärtsilä 31 engines could support these energy-intensive sectors in the future, framing the Bermeo demonstration as the foundational validation step for those commercial pathways.

The Road to Scale

While Wärtsilä characterised the Bermeo demonstration as proof that the technology works under real-world grid conditions, the company was clear that transitioning from a single validated engine to widespread deployment requires action beyond engineering. Teir's statement pointed to the need for decisive regulation, investment clarity, and hydrogen infrastructure as the prerequisites for scaling the technology.

Wärtsilä's energy division reported a track record of 81 gigawatts of power plant capacity and more than 130 energy storage installations across 180 countries. Approximately 35% of its operating installed base is under service agreements. The company employs around 17,900 professionals globally and operates across both the marine and energy industries.

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